ATX header folding doesn't work

[mickmcq]

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I don't see an option to open an issue so I'm writing it here.

When I :set ft=quarto, it breaks the folding of ATX headings (those are the # for level one, ## for level two, and so forth headings). If I :set ft=rmarkdown, the folding of ATX headings works correctly, but I lose code highlighting in R chunks. I keep switching back and forth between the two filetypes depending on what I'm doing, but it seems that quarto-vim must be breaking some functionality from vim-rmarkdown.